Method for synthetically producing ammonia



GJEUIBLG' JFRIJEJDRIGH UHDJE, 03E JBOVINGHAUSJEN, GERMANY.

METHOD FOR SYNTHETICALLY PRODUCING AMMONIA.

llllo Drawing". Application filed May 28, 1926, Serial No. 112.409, and. in Germany June t, 11925.

This invention relates to processes of synthetically producing ammonia and it comprises a. process in which the usual gases used in the synthesis of ammonia are passed over a catalyst comprising the reaction product of a complex alkali metal iron cyanide compound and a hydrolizable metal salt such as aluminum chloride.

The use of complex iron cyanide compounds for instance, t'erro-l'erri-cyanide. otherwise known as Turnbulls blue or terri lerro-cyanide, usually spoken of as llerlin blue has been suggested in the synthesis of ammonia. These con'iplex iron con'lpounds contain iron both as part of a 'com plcx radical and in an ionizable or so-called exlraadical c onditionh in use. these complex iron cyanidesahove referred to are not very satisfactory. Unly small yields of ammonia are obtained tl'irough their use. The reason for this is most probably because these iron compounds are ditlicultly dried. In fact it is impossible to completely dry these iron compounds for the reason that at the high dryingtemperature necessary almost complete dissociation of the molecules takes place before all of the water is removed. Therefore it has been necessary to use these catalysts in a Wet condition. and it is well known that water exerts a detrimental eilect on the catalytic activity of the complex iron compounds above mentioned.

l have discovered that it is possible to build up complex iron cyanide compounds which may be completely dried without dissoc-iation and hence ruination olithe catalyst taking place..- lin the compounds which l have prepared and which ll shall describe, l have found it possible to remove the water from them complctel at temperatures below the temperature oil issociation ot the compounds. uhs stated it is impossible to completely remove the water from ferro-iterricyanide or terri-lerro-cyanide without some dissociation taking place.

Since ll can completely dry my new catalyst without experiencing any dissociatlon, it will be apparent that the disturbing influence of .water in the synthesis of ammonia with iron compounds is completely obviated.

According to my invention, ll substitute "for the ionizable or ,extrwradical iron in 't'erro-ferri-cyanide for instance, a metal such as aluminum which so changes the con'iplex ironmolecule that it is possible to dry the material at temperatures below the dissociation temperature completely. l find it particularly advantageous to prepare my new catalyst by reacting easily hydroli'lzed metal salts with a complex alkali metal iron cyanide compound such as potassium lerro cyanide or potassium ferri-cyanide. ln'carrying out my process, I make up a. solution or" potassium term-cyanide or Terri-cyanide in water and add the solution so prepared to a dilute hot solution of aluminum chloride. The resulting solution is then heated. As a result of the heating, the

aluminum chloride of course, hydrolizes to liberate free hydrochloric acid. The hydrochloric acid converts the potassium ferroor ferri-cyanide into a complex iron'cyanide compound somewhat like Berlin blue or l'erri-ferro-cyanido which, of course, contains ionizable iron. The aluminum hydroxide liberated as one of the hydrolysis products reacts with the complex iron cyanide compound formed to give a complex iron cyanide, in which the ionizable iron is replaced by aluminum. The whole solution, after the formation of the complex aluminum iron cyanide compound is thereafter evaporated to dryness with stirring and the resulting materia-l may be used as the catalyst. Customarily I employ equivalent molecule quantities of aluminum chloride and potassium terroor ferri-cyanide although an excess of of the potassium compound may be use The hydrolizable metal salt reacted with the complex alkali metal iron cyanide must be of such a nature that the resulting complex iron cyanide compound can be dried completely to free it fromuvater Without dissociation.

7 I claim:

1. lln theprocess of synthetically producproduct of a complex alkali metal iron cya- 10 nide compound and aluminum chloride.

3. In the process of synthetically producing ammonia, the step which comprises contacting the ammonia forming gases with a catalyst comprising the dried reaction product of a complex potassium iron cyanide compound with aluminum chloride.

GEORG FRIEDRICH UHDE. 

